The Marvel Cinematic Universe is a huge mass of characters with crossovers, meetings, and fun discoveries for all. One match up that fans would like to see, but likely never will, is Guardians of the Galaxy meets the Avengers.
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Super Hero Hype shares director James Gunn's thoughts on the matter. He admits that because they're in a shared universe, obviously the movements of one team on Earth will affect the surrounding galaxies.
It's like the Butterfly Effect, except for instead of causing a tsunami a continent away, it causes a civil war two solar systems over. It's basic comic book 101.
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Still, from a movie standpoint Gunn explains that there was a decision about how much interaction the Guardians of the Galaxy would have with other franchises. "[R]egarding the bigger picture, we all agreed on one thing, and that was to keep huge chunks of the Guardians separate from the Marvel heroes of earth, because they have a whole galaxy to explore," Gunn wrote in a Facebook post.
This isn't to say that they will never meet up but it's far from likely. The Guardians are in space exploring and protecting the galaxy from being overrun with evil, whereas the Avengers are having a hard enough time making sure their home turf isn't overrun with mistakes from their past.
Avengers: Age of Ultron comes out May 1, 2015. Guardians of the Galaxy 2 is currently looking at being released in May of 2017.